BARNSTABLE — After a final hearing Thursday, the first trial of a father and son charged with the 2009 murder of Joseph F. Tomaselli Jr. is set to move forward April 8 in Barnstable Superior Court.

William Horton, 74, and his son, Philip Horton, 27, allegedly shot Tomaselli, 24, in the head, killing him as he sat in a parked truck in South Yarmouth on April 19, 2009.

The two defendants will be tried separately, with William Horton on trial first. Philip Horton is scheduled to go to trial May 12.

Shortly after the shooting, teenagers who discovered Tomaselli's body told the Times they had heard a "firework" about 10 minutes before finding him. One of their friends also had seen a man wearing a baseball cap walking a black dog nearby, the teens said.

The police soon focused on the Horton family, according to an affidavit filed in support of an arrest warrant in the case.

Phillip Horton owed Tomaselli money for marijuana and lured him to the parking lot, where William Horton shot him, according to police.

According to the police affidavit, Phillip Horton and Tomaselli were involved in a dispute over a substantial amount of marijuana that had disappeared. Phillip Horton told Tomaselli that police must have confiscated the marijuana while the car was impounded after a traffic stop but Tomaselli did not believe him, according to the affidavit.

The Hortons were arrested nearly two years after Tomaselli was killed in the midst of a drug investigation that included wiretapped telephone conversations that police interpreted as being related to the murder. At the time of their arrest Phillip Horton was living in Florida and William Horton was living in Dennis.

The case has lingered for several years as prosecutors and defense attorneys sparred over the evidence, including a photo identification of a dog and wiretapped conversations and text messages that were tied up in an unrelated case before the state Supreme Judicial Court.

In August the state's highest court ruled in a Berskhire County case that a Superior Court judge had the authority to issue warrants allowing the interception of cellphone calls and texts. In September, a single justice denied an appeal of a Barnstable Superior Court judge's denial of a motion to suppress evidence in the Tomaselli case on the same grounds.

Defense attorneys have argued that the drug investigation was a ruse to collect information for the murder investigation and the warrants for the wiretaps were not properly obtained. In addition to the recorded conversations and texts, police interviewed acquaintances of the two men who said Phillip Horton had said Tomaselli was dead before police had informed family members and that the two men had discussed killing each other at separate times.

Colleen Duarte, who is representing Phillip Horton, declined to comment on the specifics of the case Thursday.

"Many, many of the commonwealth's witnesses have a great deal of baggage," William Horton's lawyer, Drew Segadelli, said Thursday, referring to criminal histories of individuals expected to testify in the case.

Segadelli said there are a large number of witnesses and he expected the trial would last more than a week.